1. Field of the Invention
The present invention relates to a display device and a method of fabricating a display device, and more particularly, to a liquid crystal display device and a method of fabricating a liquid crystal display device having a reduced profile.
2. Description of the Related Art
In general, a liquid crystal display (LCD) device includes a first substrate, a second substrate, and a liquid crystal material disposed between the first substrate and the second substrate. In addition, a backlight assembly is arranged at a lower portion of an LCD panel to irradiate light. One of the first and second substrates is a thin film transistor substrate (TFT substrate) and the other is a color filter substrate. The TFT substrate includes gate bus lines and data bus lines that are formed on an inner surface of the transparent substrate in a matrix configuration. Thin film transistors (TFTs) function as switching devices and are formed at intersections between the gate bus lines and the data bus lines, and pixel electrodes that electrically contact drain electrodes of the TFTs are formed in unit pixel regions provided by the gate bus lines and the data bus lines. The color filter substrate includes a transparent substrate, a black matrix (BM) formed on an inner surface of the transparent substrate, a color filter layer, and a common electrode.
Operation of the LCD device includes a driving circuit that supplies a voltage to the gate bus lines and the data bus lines of the LCD device. As the voltage is supplied to the gate bus lines, the TFTs disposed at the intersections between the gate lines and the data lines to which the voltage is supplied, are turned ON or OFF. Then, an electric field is induced to the liquid crystal material by a voltage supplied to the pixel electrode via the TFTs and a voltage supplied to the common electrode. Accordingly, orientation of liquid crystal molecules of the liquid crystal material is changed in unit pixel regions. As a result, transmission characteristics of the liquid crystal material is changed in predetermined ones of the unit pixel regions in which the orientation of the liquid crystal molecules is changed. Thus, a predetermined color is displayed through the color filter of the color filter substrate.
FIG. 1 is a cross sectional view of a TFT substrate according to the related art. In FIG. 1, a gate electrode 102 is formed on a transparent substrate 101, and a gate insulating film 103 is grown on the gate electrode 102 by a plasma enhanced chemical vapor deposition (PECVD). An amorphous silicon layer and a phosphorous-doped amorphous silicon layer are sequentially deposited and patterned using a photolithography process to form a channel layer 104 consisting of an active layer 104a and ohmic contact layers 104b. In addition, a polarizing plate 108 is positioned on the transparent substrate 101 to polarize ambient light and transmit only light that vibrates in a specific direction.
A metal layer is deposited on the substrate 101 including the channel layer 104, and then patterned by a photolithography process to form source and drain electrodes 105 and 110 that contact with the ohmic contact layers 104b. Then, a passivation film 106 of an inorganic film is formed on the substrate 101, and a pixel electrode 107 is formed on the passivation film 106. The pixel electrode 107 is formed of indium tin oxide (ITO).
FIG. 2 is a cross sectional view of a color filter substrate according to the related art. In FIG. 2, the color filter layer of the color filter substrate is formed by a pigment dispersion method that includes coating a photoresist film containing carbon black and titanium oxide, which have light-shielding properties, on a transparent insulating substrate 201. Next, portions of the photoresist film are exposed to light using a mask to form a predetermined pattern. Then, the photoresist film is developed to remove the exposed portion of the photoresist film and remaining portions of the photoresist film that are patterned after the completion of the developing process are hardened to form the black matrix 202.
Then, a photoresist film of azo-based red pigment is coated on the substrate 201 upon which the black matrix 202 has been previously formed, and portions are exposed to light using a mask to form a predetermined pattern. Then, the photoresist film is developed to remove the exposed portion of the photoresist film and remaining portions of the photoresist film are hardened to form a red color filter. Using the same method as the formation of the red color filter, a green color filter and a blue color filter are sequentially formed on the substrate, thereby forming a color filter layer 203. Then, a transparent conductive film is deposited on an entire surface of the substrate 201 to form a common electrode 204. In addition, a polarizing plate 205 is positioned on the substrate 201 to polarize ambient light and transmit only light that vibrates in a specific direction.
The color filter substrate and the TFT substrate are bonded to each other with a gap therebetween maintained by spacers. Then, the liquid crystal material is injected into a space between the bonded substrates, thereby fabricating a liquid crystal module.
FIG. 3 is a cross sectional view of a polarizing plate according to the related art. In FIG. 3, the polarizing plates 108 and 205 of FIGS. 1 and 2, respectively, include a polarization film 301 made of polyvinyl alcohol. For example, a thin polyvinyl alcohol film is expanded while being heated, and then soaked in a solution called ink that contains a large amount of iodic acid. During the soaking process, the thin polyvinyl alcohol film absorbs the iodic acid to acquire a polarization function. Alternatively, in addition to the polyvinyl alcohol, polyvinylbutyral film into which ionic acid is absorbed, or a uniaxially extended polyvinyl into which dichroic dye is absorbed can be used.
In order to protect the polarization-functional film 301, protective films 305 and 306 are further formed on upper and lower surfaces of the polarization-functional film 301. Furthermore, each of the polarizing plates 108 and 205 of FIGS. 1 and 2, respectively, includes an adhesive film 304 adhering to the glass substrate and a protective film 303 provided on the protective film 305, for preventing the generation of static electricity. However, foreign particles may be interposed between the polarizing plate 108 and 205 (in FIGS. 1 and 2, respectively) and the color filter substrate and/or TFT substrate when the polarizing plates are adhered to the outer surfaces of the TFT substrate and the color filter substrate. The foreign particles complicate the fabrication process since the polarizing plates must be separated from the respective substrate, cleaned, and reattached. Moreover, the polarizing plates adhered to the outer surfaces of the TFT and color filter substrates increase an overall thickness of the LCD device.